Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 281140
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
440 AM PDT Fri Apr 28 2017

Updated AVIATION Section

.DISCUSSION...Low clouds are piled up on the Umpqua divide and the
Siskiyous at this time, with clear skies to the south of the
Siskiyous, and a gap of clear skies roughly north of Gold Hill.
This cloud deck is keeping the cloud covered areas in the lower to
mid 40s, and with models showing the cloud covering continuing
into the morning it looks like most of the west valleys will be
spared a frost this morning. An upper level ridge builds into the
region through the day with offshore flow strengthening. this will
bring a Chetco effect to the extreme southern coast, and have
bumped up temperatures in that area to account for this. The
thermal trough remains in place on the coast with offshore flow
spreading across the east side by Saturday morning. with the
thermal trough moving inland and the preceding strong offshore
flow, Saturday will see around a ten degree warm up from Friday.
The ridge flattens and a northwest zonal flow brings a weak front
in Saturday night. Most of the precipitation will be from the
Cascades and west as the front dissipates over the region. The
upper ridge then builds again with offshore flow, warming and
drying returning Monday. Sven

&&

.AVIATION...28/12Z TAF CYCLE...Moisture in northwest low level flow
continues to bank up against higher terrain, especially northwest-
facing slopes this morning. High terrain will be partially obscured
with areas of MVFR ceilings especially near the Umpqua Basin/Divide,
over the Cascades/Siskiyous and over portions of the East Side this
morning, then ceilings should lift to VFR and clear out with just
some fair-weather clouds after about 16-17z. Ceilings have been
LIFR at KOTH, but these should be temporary through about
16z with VFR prevailing thereafter. -Spilde

&&

.MARINE....Updated 230 AM PDT Friday, 28 April 2017...High
pressure will build over the area today with a thermal trough
along the coast. This will bring strengthening north winds and
steepening seas to the coastal waters, highest south of Cape Blanco.
Seas may reach 10 feet in some areas in the expansion fan
about 10 miles off the coast and south of Gold Beach. Farther
north, winds and seas won`t be as high, but seas could be steep
enough to cause a hazard to small craft. So, we have expanded the
advisory northward a bit. The thermal trough and the high will
both weaken allowing winds and seas to subside Friday night into
Saturday, then a feeble cold front will slip through Saturday night
into Sunday morning. High pressure will rebuild behind the front and
another thermal trough will set up next week with and extended
period of small craft advisory north winds and steep seas. Right
now, early indications are that the thermal trough could become
quite strong toward the end of next week. But, it`s still a
little early to say with much confidence if this pattern will
be strong enough for northerly gales. We`ll be monitoring this
closely through the weekend and into next week. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.

CA...None.

Pacific Coastal Waters...Small Craft Advisory from 11 AM this morning to 2 AM PDT
     Saturday for PZZ356.
     Small Craft Advisory for hazardous seas from 2 PM this afternoon
     to 2 AM PDT Saturday for PZZ350-356-370.
     Small Craft Advisory until 2 AM PDT Saturday for PZZ376.
     Small Craft Advisory for hazardous seas from 2 PM this afternoon
     to 8 AM PDT Saturday for PZZ376.
     Small Craft Advisory from 2 PM this afternoon to 2 AM PDT
     Saturday for PZZ350.

$$


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